1. Field of the Invention
The present invention relates to an additional information superposing method of superposing additional information on an information signal which is provided with it being recorded on a recording medium such as a DVD (Digital Video Disc) and so on or an information signal transmitted through a transmission medium such as internet and broadcasting media and so on, an information signal copy control method of controlling a copy generation of an information signal by using additional information added to the information signal, an information signal output device and an information signal recording device.
2. Description of the Related Art
In recent years, with the spread of digital contents such as internet and digital video disk or the like, there arises a problem of piracy that the digital contents are copied illegally. Therefore, in order to cope with this problem, it is considered that information for controlling a copy is added to the digital contents and the illegal copy is prevented by using the additional information.
As for the control to prevent the copy, two cases are considered such that copy is not permitted at all according to an information source and that copy is permitted once but the obtained copy is forbidden to be copied again (generation limit copy control method). The former case is applied to an original software such as a DVD-ROM which is produced and dealt by a contents maker. The latter generation limit copy control method is applied to information which is broadcasted in broadcasting media, for example.
In the case of the generation limit copy control method, a system which is capable of controlling the copy generation effectively is desired. As the copy control information system which is capable of managing the copy generation, a CGMS (Copy Generation Management System) and a method using an electronic watermarking process are suggested.
The electronic watermarking process embeds information as a noise into a portion which exists in image data or music data and is not important for human perceptivity, namely, a portion which is not redundant with respect to music or image. Additional information, which was embedded into image data or music data by such an electronic watermarking process, was hardly removed from the image data or music data. Meanwhile, even after image data or music data are subject to a filtering process or data compressing process, the additional information as electronic watermarking information embedded thereinto can be detected from the image data or music data.
In the case of the copy control method using the electronic watermarking process, additional information to be embedded represents the following four states:
(1) xe2x80x9cCopy Freexe2x80x9d;
(2) xe2x80x9cOne Copyxe2x80x9d;
(3) xe2x80x9cNo more Copyxe2x80x9d; and
(4) xe2x80x9cNever Copyxe2x80x9d,
namely, it represents copy generation of image data or music data on which the electronic watermarking information was superposed and the copy limit state.
(1) xe2x80x9cCopy Freexe2x80x9d represents that music data or image data can be copied freely. (2) xe2x80x9cOne Copyxe2x80x9d represents that music data or image data can be copied only once. (3) xe2x80x9cNo More Copyxe2x80x9d represents that music data or image data are obtained from the music data or image data in the state of (2) xe2x80x9cOne Copyxe2x80x9d, and they are not allowed to be copied again. (4) xe2x80x9cNever Copyxe2x80x9d represents that music data or image data are never allowed to be copied.
In the case where the electronic watermarking information which was superposed on image data or music data is xe2x80x9cOne Copyxe2x80x9d, a judgment is made that the image data or music data can be copied and recorded and the recording is executed in a recording device which can execute the electronic watermarking process (namely, copy limit process), but the electronic watermarking information which was rewritten into xe2x80x9cNo More Copyxe2x80x9d is superposed on the recorded image data or music data. In the case where the electronic watermarking information which was superposed on the image data or music data to be recorded is xe2x80x9cNo More Copyxe2x80x9d, a judgment is made that the image data or music data are not allowed to be copied and recorded and the recording is forbidden in the recording device which can execute the electronic watermarking process.
In the CGMS system, in the case of an analog image signal, for example, additional information of 2 bits for copy control is superposed on specified one horizontal period within the vertical blanking period, and in the case of a digital image signal, additional information of 2 bits for copy control is added to the digital image data so that the data are transmitted.
The contents of the information of 2 bits in the CGMS system (hereinafter, referred to as CGMS information) are:
[00] . . . copy free;
[10] . . . one copy (copy by only one generation); and
[11] . . . never copy.
In the CGMS system, the above-mentioned state xe2x80x9cNo More Copyxe2x80x9ddoes not exist.
In the case where the CGMS information added to image information is [10], a judgment is made that the image information can be copied and recorded and the recording is executed in a recording device which can cope with CGMS, but the CGMS information which was rewritten into [11] is added to the recorded image signal. In the case where the CGMS information added to the image information to be recorded is [11], a judgment is made that the image signal is not allowed to be copied and recorded and the recording is forbidden in the recording device which can cope with CGMS.
Incidentally, in the case where the copy of an analog image signal or digital image signal is controlled by the CGMS system as mentioned above, the CGMS information of 2 bits is added to a specified position which is separated from a signal forming an image.
For this reason, in the case where, for example, the digital image signal to which the CGMS information was added is used, it is considered that when the digital image signal is converted into an analog image signal so as to be utilized, the CGMS information is possibly lost.
In this case, even when the digital image signal is forbidden to be copied by the CGMS information, by converting the digital image signal into an analog image signal, it becomes possible that the analog image signal is freely copied.
Therefore, as the additional information for copy control, it is considered that electronic watermarking information is superposed on information signals such as an analog image signal and a digital image signal so as to be provided. As mentioned above, since the electronic watermarking information is superposed on an information signal, it is difficult to remove the electronic watermarking information from the information signal or alter it.
In addition, since the electronic watermarking information can represent a copy generation and copy limit state of an information signal as mentioned above, in the recording device which can cope with the electronic watermarking process, the copy of the information signal can be controlled securely and properly based on the electronic watermarking information.
However, as mentioned above, in the case where the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d is superposed on an information signal, the information signal is copied based on the electronic watermarking information in the recording device which can cope with the electronic watermarking process. However, since the copied information signal is forbidden to be copied again, the electronic watermarking information added to the information signal to be recorded should be rewritten into xe2x80x9cNo More Copyxe2x80x9d.
In this case, the following two methods are considered. In one method, the electronic watermarking information representing xe2x80x9cNo More Copyxe2x80x9d is overwritten on the information signal on which the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d was superposed. In the other method, after the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d is deleted from the information signal on which the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d was superposed, the electronic watermarking information representing xe2x80x9cNo More Copyxe2x80x9d is newly superposed on the information signal.
However, in the former method, since the electronic watermarking information representing xe2x80x9cNo More Copyxe2x80x9d is overwritten on the information signal on which the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d was superposed, an image which is formed by the image signal is possibly deteriorated.
In the latter method, the electronic watermarking information for deletion, which is the completely same as the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d superposed on an information signal, is generated at timing completely same as the electronic watermarking information representing xe2x80x9cOne Copyxe2x80x9d, and the electronic watermarking information for deletion is subtracted from the information signal so that the electronic watermarking information superposed on the information signal can be deleted.
However, it is difficult to generate the same electronic watermarking information in the information signal on which the electronic watermarking information was superposed at the timing completely same as the superposing of the electronic watermarking information. Particularly in the case where the information signal on which the electronic watermarking information was superposed is an analog signal, the timing is delayed easily, and the information signal is occasionally deteriorated by subtracting the electronic watermarking information.
In such points in view, it is an object of the present invention to provide an additional information superposing method of superposing different two pieces of additional information on an information signal with deterioration of the information signal being suppressed minimumly so as to be capable of transmitting the information signal, an information signal copy control method using additional information superposed on an information signal, an information signal output device and an information signal recording device.
In order to solve the above problem, a method in accordance with the invention for superposing second additional information as electronic watermarking information on an information signal on which first additional information as electronic watermarking information was superposed, is characterized in that the information signal is divided into a first area and a second area, the first additional information is superposed on the first area and the second additional information is superposed on the second area.
According to the additional information superposing method of the invention, the information signal is divided into the first area and the second area, and the first additional information and the second additional information as electronic watermarking information are superposed in the different areas.
As a result, the different two pieces of information are superposed on one information signal, and thus the information signal can be transmitted so that the two pieces of information can be extracted. Moreover, since the two pieces of information are not superposed on one area of the information signal, deterioration of the information signal, which is caused by superposing the additional information does not become serious.
In addition, according to another aspect of the invention, an additional information superposing method is characterized in that:
the first additional information and second additional information are information for limiting a copy generation of the information signal; and
the first additional information represents a state before the copy generation is limited, and the second additional information represents a state after the copy generation is limited.
According to the additional information superposing method of the invention, for example, the information representing xe2x80x9cCopy Oncexe2x80x9d is superposed on the first area of the information signal, and when the information signal is recorded on a recording medium, the information representing xe2x80x9cNever Copyxe2x80x9d is superposed on the second area of the information signal.
As a result, the copy generation of the information signal can be limited securely and properly based on the information before the copy generation is limited added to the first area of the information signal and the information after the copy generation is limited added to the second area. Moreover, since the information before the copy generation is limited (first additional information) and the information after the copy generation is limited (second additional information) are not superposed on one area of the information signal, the deterioration of the information signal, which is caused by superposing different pieces of additional information, can be prevented.
In addition, according to another aspect of the invention, an additional information superposing method is characterized in that the first area and second area are set as areas for each predetermined time length of the information signal.
According to the additional information superposing method of the invention, the first area and second area of the information signal on which the additional information is superposed are determined by a time length of the information signal in a manner that the information signal is divided by time such that the first 1 second is for the first area and the next 1 second is the for the second area, or the first 1 second is for the first area and 2 seconds are paused and the next 1 second is for the second area.
As a result, the first area and second area are determined in the time direction of the information signal, and the first additional information is superposed on the first area and the second additional information is superposed on the second area so that the information signal can be transmitted.
In addition, according to another embodiment of the invention, an additional information superposing method is characterized in that the first area and second area are set as areas for each predetermined data amount of the information signal.
According to the additional information superposing method of the invention, the first area and second area on which the additional information is superposed are determined based on predetermined data amount in a manner that in the case where the information signal is a digital signal, a block which is a processing unit of the digital signal is used as unit so that the first 3 blocks are for the first area and the next 3 blocks are for the second area.
As a result, the first area and second area are determined based on the data amount of the information signal, and the first additional information is superposed on the first area and the second additional information is superposed on the second area so that the information signal can be transmitted.
In addition, according to an additional embodiment of the invention, an additional information superposing method is characterized in that:
the information signal is an image signal; and
the first area and second area are formed in a time direction by using a frame or field as unit.
According to the additional information superposing method, the information signal is an image signal, and the first area and second area are determined by using a frame or field as unit in a manner that the first area and second area are set alternatively per 1 frame or 1 field.
As a result, the first area and second area are determined by using a frame or field of the image signal as unit, and the first additional information is superposed on the first area and the second additional information is superposed on the second area so that the image signal can be transmitted.
In addition, according to yet another embodiment of the invention, an additional information superposing method is characterized in that:
the information signal is an image signal; and
the first area and second area are formed separately within one frame or one field.
According to the additional information superposing method the information signal is an image signal, and the first area and second area are determined in an interval direction of the image signal in a manner that the upper half portion of each frame is for the first area and the lower half portion is for the second area or the upper half portion of continuous plural frames is for the first area and the lower half portion is for the second area.
As a result, the first area and second area are determined in a spatial direction of the image signal, and the first additional information is superposed on the first area and the second additional information is superposed on the second area so that the image signal can be transmitted.
The first additional information of the first area which is superposed on the information signal as mentioned above is monitored, or the second additional information of the second area is monitored or the first additional information of the first area and the second additional information of the second area are monitored so that a judgment is made as to whether or not the information signal can be copied. Then, the recording can be controlled properly, and the second additional information is superposed on the second area if necessary so that the information signal can be transmitted.